In February 1935, the year of King George V’s silver jubilee, a chimpanzee at London Zoo called Boo-Boo gave birth to a baby daughter. A couple of months later, a little blonde-haired girl was given a soft-toy replica of the zoo’s new arrival to mark her first birthday. This was Jane Goodall’s first recorded encounter with a chimp.

[Goodall’s] research on a community of chimpanzees in Tanzania revolutionised our understanding of these primates, our closest living relatives, and challenged deepset ideas of what it means to be human. She then packed in her fieldwork to become an activist, campaigning tirelessly for a more enlightened attitude towards animals and the environment. Along the way she has received nearly 50 honorary degrees, and became a UN Messenger of Peace in 2002 and Dame Jane in 2004.

Though I have only crossed London to meet her, I am struck by the sudden feeling that I have reached the end of some epic, Henry Stanley-like quest… “Dr Goodall?” As I reach out to shake a slender hand, the words “I presume” pop into my head. I suppress them.

I follow her into the front room and she politely offers me tea or coffee. There is a sofa beneath the bay window and next to it – as if only just put aside – a large book. I pick up The Chimpanzees of Gombe: Patterns of behavior, Goodall’s magnum opus published in 1986. I flip through its characterful portraits of the Gombe chimps, many of them – like David Greybeard – now household names.

Goodall sits down neatly on the sofa with her back to the bright sun. This is a brief pause in her whirlwind travel schedule of more than 300 days a year, but she displays few signs of weariness – worldly or otherwise. She has just been going through proofs of her updated book Seeds of Hope, the first edition of which was troubled by allegations of plagiarism. I don’t want to broach the subject so early in the interview, so I ask instead about her childhood, which I sense is of great importance to understanding Goodall.

Having seen a photograph of that doting little girl clutching Jubilee, her somewhat scruffy birthday chimp, I love the idea that this fluffy character influenced what Goodall would go on to achieve. On this, however, she sets me straight. When she first ventured to Africa in 1957, Goodall says, it had never occurred to her to work with chimpanzees. Rather, she had a far less specific and more romantic dream inspired by fictional characters from the books she had read as a child, notably Dr Dolittle and Tarzan. “I never wanted to be a scientist per se,” she says. “I wanted to be a naturalist.”

Goodall tells a story from her childhood that demonstrates how fixated she was by the Africa of her imagination. As a special treat, her mother, Vanne, had taken her to the cinema to see her first Tarzan film. When the curtains drew back to reveal Johnny Weissmuller in the starring role, however, the young Goodall burst into a fit of hysterical tears. In the quiet of the foyer, she composed herself and told her mother firmly: “That is not Tarzan.”

When she describes her earliest experiences of Africa, however, they don’t sound all that different from the jungles of her dreams. Not long after arriving in Kenya, Goodall captured the attention of Louis Leakey, the eminent palaeoanthropologist and curator of the Coryndon Museum in Nairobi. Within hours of meeting, she had so impressed him with her knowledge of natural history that he had offered her a job. Within months, Leakey and his wife, Mary, set out on an expedition to Olduvai Gorge in what is now northern Tanzania, and Goodall went too. The place was teeming with wildlife.

“There were lions and rhinos and giraffes – I mean, everything was there,” she recalls with a flash of excitement. “I often think that’s one of the most magical times of my whole life.”

It was while scouring this ancient landscape for evidence of early humans and other hominids that Leakey first mentioned the idea of establishing a complementary study on wild chimpanzees to the west, at the Gombe Stream Chimpanzee Reserve on the edge of Lake Tanganyika. Three years later, in 1960, Goodall entered the reserve to begin her research.

There had only ever been one concerted attempt to study chimps in the wild – and that scientist “had a trail of 22 porters”, Goodall says with a hint of pride in her voice. For the first few months in Gombe, it was just her, her mother and a single hired assistant. “I wanted to be alone,” she says, “but I wasn’t allowed.”

Goodall pauses, revisiting that period in her mind. “I’ll never forget going along the shoreline of Lake Tanganyika, then looking up…”

Up there, in the densely forested valleys that funnel streams off steep hills to the water’s edge, were the chimpanzees she had come to study. With the assistance of a game warden who acted as escort, Goodall and her mother put up their ex-army tent. “If you wanted air to come in, you just rolled up the sides and tied them with tape,” she says. “Well, the air came in, but the spiders, scorpions and snakes came in as well.”

Although her mother was terrified – “You know I’m afraid of spiders!” – Goodall was apparently fearless, setting off up the slopes to explore her new home. “I sat up there and just couldn’t imagine I was there. It seemed absolutely unreal.”

The picture Goodall paints – a folding camp bed beside a palm tree in a forest clearing beneath a bright moon, the sound of baboons barking in the distance – could have come straight from an Edgar Rice Burroughs novel. I wonder if the realisation of so fantastical a childhood dream has helped her stay connected to her youth – but again she sets me straight. Rather it is The Birches, the home near Bournemouth in which she grew up: when not travelling, this is where Goodall still returns, to “all my childhood books, the trees I climbed as a child, the cliffs where I walked… I am blessed in this way.”

During her first stint in the field, Goodall struggled to get close to the chimps. However, the individual she named David Greybeard proved a particular inspiration, showing her a side to chimpanzees nobody had ever documented before. In late October 1960, she watched David from a distance as he gnawed away at the freshly killed corpse of what was probably a baby bush pig – an observation that ran counter to the then-widespread assumption that chimps were strict vegetarians.

A few days later, Goodall witnessed David making and using a tool to feed on ants. I ask her to describe this moment in detail: “There was vegetation in the way and David had his back to me… so what I saw was the hand picking up the tool. I saw the movements. And I saw it was obvious he was eating…”

Once David had moved off, Goodall went to investigate and discovered long stalks of grass lying around. Picking a stalk up, she pushed it into one of the narrow entrance holes to the ant colony. The disturbance caused ants to emerge. The chimps, presumably, would then lick them off the grass. After subsequent, clearer sightings of this behaviour, Goodall went to Leakey with the discovery.

“I knew it was very important because I’d been around Leakey long enough,” she says. At that point, most people believed humans were the only species capable of making and using tools. In response to Goodall’s observations of David and others, Leakey famously declared: “Now we must redefine ‘tool’, redefine ‘man’, or accept chimpanzees as humans.”

I am suddenly aware that Goodall is watching me, back perfectly upright, hands in her lap. She keeps very still, her soft green eyes studying my face as she waits patiently for my next question. I feel a peculiar, strangely comforting empathy with David Greybeard and the other Gombe chimps.

Despite Leakey’s excitement over Goodall’s early findings, not everyone was ready to embrace them. In late 1961, she arrived in Cambridge, where Leakey had used his connections to enrol her for a doctorate – not something Goodall wanted to do. “I was only doing this thesis for Leakey’s sake. I’d never had an ambition to be a scientist and be part of academia.”

The patronising treatment Goodall received at the hands of her mainly male colleagues can hardly have endeared her to the academic lifestyle. She was criticised for giving her study-animals names and personalities. “I didn’t give them personalities, I merely described their personalities,” she counters. As for Goodall’s reported discovery that chimps used tools: “Some scientists actually said I must have taught them.” She laughs. “That would have been fabulous if I could have done that.”

I try to imagine receiving this kind of dismissive treatment, and suspect I would have been infuriated, then crushed. Not Goodall. She says she simply knew that she was right and her critics were wrong. I ask where this conviction came from and, as an explanation, she returns to her youth.

“My mother always taught us that if people don’t agree with you, the important thing is to listen to them. But if you’ve listened to them carefully and you still think that you’re right, then you must have the courage of your convictions.”

So when her Cambridge colleagues told her she couldn’t talk about chimps having personality, mind and emotion, she begged to differ – because of Rusty the black mongrel. “Rusty had taught me otherwise. If you spend time with animals, you’re not going to betray them by taking away something which is theirs.”

Rusty, I discover, was one of two dogs with whom Goodall became friendly in her early teens at The Birches. The other, Budleigh, was a beautiful long-haired collie belonging to the owner of the local sweetshop. “Collies are meant to be bright but he wasn’t,” Goodall says, recalling how Budleigh proved incapable of learning to shake hands.

One day, though, as Goodall continued her efforts to train “Buds”, Rusty the mongrel (watching at a distance) raised his paw. “From that moment I realised Rusty was brilliantly intelligent because, even though I wasn’t teaching him, he’d learned by observing my teaching of Buds.”

I am struck by what Goodall did next. The young teenager imagined herself inside Rusty’s mind, she says, in an effort to see the world from his perspective and relive the intellectual feat he’d just performed. There are not many children I know who’d do this, I suggest. She considers for a moment: “Probably not.”

If her Cambridge colleagues had been patronising, it was nothing compared to the treatment she received at a symposium on primates held at the Zoological Society of London in April 1962. “I gave my first scientific presentation and was terrified, says Goodall. “I practised for hours,” she says. “I was determined not to read and not to say ‘er’ or ‘um’. I have remained true to that ever since.”

After three days of talks, the meeting came to a close with a speech by Sir Solly Zuckerman, an anatomist who had studied monkeys in Africa, and gone on to become secretary of the Society and chief science adviser to the Ministry of Defence. Although Goodall had been well received, Zuckerman took the opportunity to fire a volley of pointed comments at the twentysomething newcomer.

“There are those who are here and who prefer anecdote – and what I must confess I regard as sometimes unbounded speculation,” he told his audience, as recounted in Dale Peterson’s biography of Goodall, The Woman Who Redefined Man. “In scientific work it is far safer to base one’s major conclusions and generalisations on a concordant and large body of data than on a few contradictory and isolated observations, the explanation of which sometimes leaves a little to be desired.”

At the mention of Zuckerman, Goodall’s features sharpen slightly, and the pace of her speech quickens. She dismisses his monkey work as “rubbish”. It is the only bad word she has to say about anyone, and even then she controls the emotion almost before it has appeared.

This was not Goodall’s first run-in with Zuckerman. At the end of 1961, there had been a press conference at London Zoo to announce her preliminary findings – and she had hatched a plan to use this public platform to call for an improvement in the conditions of the captive chimps at the zoo. “There was a bare cage with a cement floor,” she explains. During the summer months, the chimps had no shade: “It got boiling hot and there was only one platform, the other had broken, so the male got that and the female had to sit on the floor. It was horrible.”

Before the meeting, over dinner with the diplomat Malcolm MacDonald (who had visited her briefly in Gombe and would become Governor-General of Kenya in 1963), Goodall shared her intention to champion the welfare of the captive chimps: “I was really excited.”

But MacDonald, with his experience as a politician, could see a flaw. Speaking out on behalf of the chimps to a packed auditorium would be a direct criticism of Zuckerman’s leadership of the zoo. “Do you think he’s going to allow a little whipper-snapper who doesn’t even have a degree to tell him he’s in the wrong?” Goodall recalls MacDonald telling her. “You’ll make an enemy for life, and you don’t want an enemy like that.”

Instead, Goodall suggested several simple changes to the chimps’ enclosure that would improve their welfare, and MacDonald worked behind the scenes to see them implemented. “What I learned then is: don’t let people lose face, don’t try to do something publicly until you’ve tried every which way to do it quietly. I’ve found that so helpful to me,” she says, particularly in places like Africa and China.

Naturally, Zuckerman took the credit for the improvements to the chimps’ enclosure. “I don’t mind two hoots as long as it gets done,” Goodall says.

A capacity for seeing the bigger picture may go some way to explaining her success as an activist. She pinpoints her transformation to 1986, and a chimpanzee conference organised by the Chicago Academy of Sciences to coincide with the publication of The Chimpanzees of Gombe. By then, she’d spent more than 25 years in the field, completed her PhD, established the Gombe Stream Research Center, got married, raised a son and made further groundbreaking observations on chimpanzee society – including insights into chimp communication, sex, mother–infant bonding, inter-community warfare and cannibalism. But at the age of 52, she walked away from the field and turned to a life on the road. “How ridiculous, really, when you think about it,” she says. “What did I think I could do, trotting around Africa with an exhibit of old pictures blown up, and bits of rock and stick?”

Her initial focus – facilitated by the Jane Goodall Institute she’d established almost a decade earlier to support her chimp research at Gombe – was to draw attention to the plight of chimpanzees more generally. In the wild, habitat destruction, the bushmeat trade and animal trafficking all posed significant threats to the species’ future – and they still do. “It is horrendous.”

Even now, China is asking African governments for chimpanzees and gorillas for entertainment, Goodall tells me. “We feel our sanctuaries, which cost us so much money, aren’t safe any more.”

I find myself being sucked into a vortex of gloom, but Goodall is always ready to offer a reason for hope – a word that crops up time and again in the titles of her many books. One reason is what she calls “the resilience of nature”; by way of illustration, she tells me about land reforms in Tanzania in the 1970s that resulted in widespread deforestation around the Gombe Stream Chimpanzee Reserve.

“When I looked down,” she recalls of one visit, “it was so totally shocking to see our little oasis of Gombe… It looked like a dust bowl: completely bare hills, overfarmed, more people living there than the land could support.”

More than half a century since she first engineered improvements to the conditions of the chimpanzees at London Zoo, Goodall is still fighting hard on behalf of captive chimps too. In the 1980s, she raised ethical concerns about their use in xenotransplanation, which led the medical community to steer away from this practice. More recently, she has worked with Francis Collins, Director of the National Institutes of Health in the US, to phase out their use of captive chimpanzees in medical research; she is delighted the US Senate voted to increase the budget available for retirement of these chimps. “We are beginning to win,” she says.

I ask Goodall if she is in favour of a blanket ban on the use of chimpanzees in medical research. “I can’t quite say that. But what I can say is that, ethically and morally, I feel it’s wrong to use them, and it’s absolutely wrong to put them in five-foot by five-foot cages.”

Goodall puts chimps at the forefront of the wider debate about the use of experimental animals. “At one time, the scientists said we’ll always need animals for this – and now we don’t,” she says. “If science really puts its mind to getting alternatives… once they do, they’re cheaper and usually safer.”

With our time almost up, I realise I haven’t asked after Mr H, the toy monkey who famously travels with her from one venue to the next. Somehow Goodall the activist doesn’t seem complete without him, and I wonder if he might join us.

Mr H stands for Mr Gary Haun, a US marine who lost his eyesight in a helicopter crash at the age of 21, then went on to became a professional magician, climb Mount Kilimanjaro, scuba, sky-dive, and much else besides. “He thought he was giving me a stuffed chimp for my birthday,” Goodall recalls – but the soft toy has a tail, so is clearly a monkey. “Gary,” she told him, as she guided his hand towards the evidence of his mistake, “I know you can’t see it… but you have no excuse.”

For the last 20 years, Goodall has kept Mr H close as a reminder of another of her reasons for hope: “The indomitable human spirit… He’s been to at least 60 countries with me, he’s been touched by at least four million people. I say that when you touch him, the inspiration rubs off.”

Goodall invites me to touch Mr H – but instead of inspiration, I have a sudden, parental panic that he might one day go missing. “I’ve nearly lost him several times but that’s the original,” she says, stroking him gently. Once, she left him on the top of a telephone kiosk in an airport and had boarded her plane before she realised. “I’ll have to get off the plane,” she explained to the attendant, adding: “You’ll have to bolt me in to keep me because I’ve left my most precious object outside.”

Still clutching Mr H, Goodall reaches into her bag and another soft toy peeps out. “This is Cow” – a gift handed to her during a recent visit to the dairyland state of Wisconsin. “I was going to give Cow to the next deserving child,” she explains, but instead she has turned her into “a spokesperson” for abused farm animals. She looks at the toy and then talks about it as if she’s giving it praise. “Cow has worked really hard – she has created I don’t know how many vegetarians, even in places like Argentina where they live on meat.”

I am reminded of something I’ve read: how Goodall, as a child, loved to arrange tea parties for her soft toys. I wonder if there are others who would like to join us – but it turns out that Jubilee, her childhood chimpanzee, is in Germany, being fitted for a jumpsuit to hold his failing stitching in place.

Goodall herself is flying to Germany in a few hours. “I’m going to Düsseldorf, then Vienna, then back to Munich… It still amazes me. Children write to me and say, ‘You taught me, you did it, I can do it too.’ So this is why I have to go on going around. Because it’s making a difference.”

When not on the move, she concentrates on her writing. In her latest book, Seeds of Hope, she and journalist Gail Hudson champion plants. But the first edition, published last year, was troubled by allegations of plagiarism, with the Washington Post identifying “at least a dozen passages borrowed without attribution, or footnotes, from a variety of websites”.

Goodall accounts for these lapses by citing her hectic work schedule and her chaotic method of note-taking: “I am not methodical enough, I guess,” she says. “In some cases, you look at my notebooks, there’s no way you can tell whether this is from talking to somebody or whether it was something I read on the internet.”

I ask if there was any naivety on her part. “Yes, there must be… I have learned. In the future, I shall be more organised even if I don’t have time,” she says. “I shall certainly make sure I know who said something or what I read or where I read it.” Goodall, though, is adamant that she did not intentionally try to pass off anyone else’s words as her own. “I don’t think anybody who knows me would accuse me of deliberate plagiarism.”

In a revised edition of Seeds of Hope, to be published this month, Goodall and Hudson have made minor changes to the text to address their critics and added a lengthy notes section. “I don’t think a book has ever been more researched than this one. The notes at the end are about as long as the book.”

I ask if she’s concerned that attention will focus on what she’s changed, rather than on the subject matter. “Looking back, it has been a godsend,” she says. “I am really happy for the sake of the plants that we’ve got it right now. I feel this is a book we can really be proud of now.”

And then she adds, “Honestly, Henry, who is going to deliberately go out to give me a bad time?” We both know it will probably happen.

Before I go, Goodall wants to show me some drawings she made as a child. They are reproduced in Me… Jane, a children’s book by Patrick McDonnell. She finds a copy amid piles of books by or about her, and flips to the relevant page. There, across a double spread, are several meticulous sketches of animals. The wing of a pterodactyl above the wing of an eagle; profiles of a cat, horse, crocodile, dog, chimpanzee and human – all to scale with their brains neatly coloured in pink pencil. “They are not very good,” she says.

I have spent the last two hours in the polite, inspiring company of a woman precisely twice my age. But as she shows me her drawings, I get the feeling I am talking to the 12-year-old Goodall. Finally, when I hold out my hand for her to shake, she spurns it and offers me something far more rewarding: a chimpanzee embrace. Her delicate arms envelop me, slowly, widely, deliberately. There is something categorically different about this hug; something that will stay with me for ever.

“Chimpanzees don’t say goodbye,” she says. I walk to the door, trying to fathom what to make of this. I turn and call out another farewell, but Goodall doesn’t reply. She has turned away from me and doesn’t look back.